192 PROTEINS AND CARBOHYDRATES 
Liebermann’s Reaction. Boil the protein solution with about 
4 ec. of concentrated hydrochloric acid. A  violet-lavender color 
will result if tryptophane is present. 
Bromine Reaction for Tryptophane. Uncombined tryptophane 
when treated with bromine water will give a violet color. 
Test for Tyrosine. Add a few drops of formol solution to concen- 
trated sulphuric acid. On warming with tyrosine, a brown red color 
is obtained, which, on addition of acetic acid becomes green. Neither 
proteins nor peptones give the reaction. (Nasse’s modification of 
Denigé’s test. Quoted from Smith, 1905.) 
Schmidt Test for Tyrosine. Dissolve by boiling in water and add 
a solution of mercuric nitrate. The red reaction is sharper if a little 
fuming nitric acid diluted in water is added. Try also the violet reaction 
with neutral iron chloride. (Quoted from Smith, 1905.) 
Precipitation Reactions. The precipitation reactions of proteins 
are important in removing them from solution and also for detecting 
them in solution. Most of the metals will precipitate them. Mercury 
will throw down a heavy white precipitate of mercury proteinate. Cop- 
per, when added to a protein solution as the sulphate, will throw down a 
bluish precipitate. Iron and lead also give heavy precipitates, the one 
with iron being dissolved by an excess of that compound. Picric acid, 
trichloracetic acid, phosphotungstic acid, tannic acid and bromine 
also form precipitates in protein solutions. 
CARBOHYDRATES 
The carbohydrates may be classified in different ways. The fol- 
lowing is a convenient method: 
I. Monosaccharides 
A. Pentoses, CsHi005 
1. Xylose 
2. Arabinose 
B. Hexoses, CeH120¢6 
1. Dextrose 
2. Levulose 
3. Galactose 
IJ. Disaccharides 
1. Sucrose 
2. Maltose 
3. Lactose 
